The 29-year-old actress and singer went from a size 16 to a size six after giving birth to David in August 2009, and said that she 'wanted her body back'.
Appearing on The Ellen DeGeneres Show, the Jenny Craig spokeswoman said, 'I just knew, after I had my baby, I just wanted my body back. Whatever body that was.
'And then I realised [that] when I was pregnant, I was like, 'Man, I was wearing the same clothes I was wearing before I was pregnant'. That was kind of like a wake-up call and I wanted to set a good example for my son.'
But she insisted that she was happy with her body before her weight loss. 'I was very comfortable. It wasn't that I couldn't do it, I just didn't see anything wrong with it,' she said. 'I still don't. I liked who I was then, and I like who I am now.'